Factors affecting the numbers of expected viable lactic acid bacteria in inoculant applicator tanks

Abstract

The application of correct numbers of viable microorganisms to forages at the time of ensiling is one of the most important factors affecting the probability of a beneficial effect from an inoculant. The objective of this study was to determine relationships between numbers of expected lactic acid bacteria (LAB) from silage inoculants in application tanks and various factors that might affect their viability. The pH and temperature of inoculant-water mixes were measured in applicator tanks (n=53) on farms in Wisconsin, Minnesota, South Dakota, and California during the corn harvest season of 2012. Samples were collected on-farm and plated on de Man, Rogosa, and Sharpe agar to enumerate LAB and establish the number of viable LAB (cfu/mL). Expected numbers of LAB were calculated from the minimum label guarantees for viable bacteria and mixing rates with water. In addition, the pH of the inoculant-water mixes at sampling, the ambient temperature at sampling, and the length of time that the samples had been in the tank were measured and obtained. The log difference between the measured and expected numbers of LAB was calculated and expressed as ΔM - E in log scale. Ambient temperature at sampling had no relationship with time in the tank or ΔM - E. Most (83%) of the inoculants had been mixed with water in the applicator tanks for <10h. For these samples, a negative linear correlation (R=0.36) existed between time that the inoculant-water mixes were in the applicators tanks and ΔM - E. The pH of the inoculant-water mixes was also negatively correlated (R=0.28) with time in the applicator tank, but pH was not related to ΔM - E. The temperatures of the inoculant-water mixtures were negatively correlated with ΔM - E (R=0.39). Seven of 8 samples whose ΔM - E were at least -0.95 or more lower than expected (equivalent of about 1 or more log concentration less than expected) had water temperatures above 35°C. These data support our previous laboratory findings and suggest that high temperatures of inoculant-water mixes have the potential to negatively affect the final application rate of some inoculants, which may affect their overall effectiveness to improve silage fermentation.

Production and utilization of silages in tropical areas with focus on Brazil

“…Mulrooney and Kung () reported that the viability of several microbial inoculants was markedly decreased when the temperature of the solution increased above 35°C. Recently, Windle and Kung () showed a negative correlation between time in the applicator tank and loss of inoculant viability in the field. Placing tanks to minimize absorption of heat from machines and the use of thermal insulation materials to protect the tank should be considered by the silage machinery industry worldwide.…”

Chemical composition, fermentative losses, and microbial counts of total mixed ration silages inoculated with differentLactobacillusspecies

“…The use of microbial inoculants in forage silages (corn, sorghum, grasses, etc. ) aims to improve fermentation and aerobic stability (Windle and Kung, 2016). According to Muck (2013), lactic acid bacteria (LAB) are the main group of microorganisms that act in the forage fermentation process and have the ability to produce lactic acid as their main fermentation product.…”

Criteria for lactic acid bacteria screening to enhance silage quality

“…The ideal temperature depends on the purpose of the selection. Generally, micro-organisms that exhibit higher optimum growing temperatures are of value in countries with a hot climate to ensure the survival of the strain when heating the silo or during the mixing and application of inoculants (Windle and Kung 2016). In regions with a cold climate, micro-organisms that have optimal growth in low temperatures are also of interest to ensure microbial growth and its action.…”